When Immigration and Customs Enforcement agents found problems last month with the citizenship status of 43 employees of the Hilton Head Island Bi-Lo store, questions were raised as to why the store didn't check out their employees more thoroughly. But, according to experts, just about any business could find itself in the same position. Properly completing citizen and identity verification forms, called the I-9 form, is all a business can, and probably should, do in attempting to thwart fraud from those seeking employment illegally, according to a local immigration law expert and the government's guidelines. "Employers are not required to be immigration experts," said Melissa Azallion, a labor and immigration lawyer with the Hilton Head office of the law firm Nexsen Pruet.